EV efficiency: translating kWh/100mi into a gasoline-equivalent L/100km
I tried to explain my EV's efficiency to a relative who only thinks in liters per 100 km, and realized there isn't a direct conversion — you have to route through the EPA's gasoline-gallon-equivalent and flip it twice.
We write the way we argue on the bench: exact factor, one sharp trap, one worked example you can re-check.
I tried to explain my EV's efficiency to a relative who only thinks in liters per 100 km, and realized there isn't a direct conversion — you have to route through the EPA's gasoline-gallon-equivalent and flip it twice.
The factor below is the one that ends the argument — write it once, then stop improvising mid-job.
The factor that settles arguments
This is the relationship our converters use. Screenshot it if you have to — just stop re-deriving it from a half-remembered blog post.
EPA gasoline-gallon-equivalent: 33.7 kWh = 1 gallon; combine with 235.215 ÷ MPG = L/100km
Write that line once at the top of your notes. Every later arithmetic step should point back to it instead of inventing a friendlier number mid-stream.
The mistake that keeps showing up
Trying to convert kWh/100mi to L/100km with a single multiplication factor, when the real path runs through a reciprocal (efficiency to MPGe) and then another reciprocal (MPGe to L/100km).
I still write the unit next to every intermediate value. It looks pedantic until it catches the one swap that would have shipped wrong.
- Write down the known value in kWh per 100 mi.
- Confirm the target unit is really L/100km-equivalent, not a similar-looking one.
- Apply the factor: EPA gasoline-gallon-equivalent: 33.7 kWh = 1 gallon; combine with 235.215 ÷ MPG = L/100km.
- Round only at the end, to the precision your tool or spec supports.
Worked example
Your EV displays 30 kWh per 100 miles, and you want a gasoline-equivalent L/100km figure to compare with a combustion car.
30 kWh/100mi → MPGe = 33.7 ÷ 0.30 = 112.3 MPGe → L/100km-e = 235.215 ÷ 112.3 = 2.09.
That's about 2.09 L/100km-equivalent — a two-step chain, not a single multiply, because it runs through a reciprocal both times.
Flip the factor once as a sanity check. If you do not land near the starting number, you mixed definitions or inverted the direction.
Quick reference table
| kWh per 100 mi | Calculation | L/100km-equivalent |
|---|---|---|
| 20 kWh/100mi | 33.7÷0.20 → 235.215÷168.5 | 1.40 L/100km-e |
| 25 kWh/100mi | 33.7÷0.25 → 235.215÷134.8 | 1.74 L/100km-e |
| 30 kWh/100mi | 33.7÷0.30 → 235.215÷112.3 | 2.09 L/100km-e |
| 40 kWh/100mi | 33.7÷0.40 → 235.215÷84.3 | 2.79 L/100km-e |
Use the table for speed once you trust the factor. Do not use it as a substitute for understanding which definition of the unit you are on.
Why the exact number matters
Cross-comparing EV and gasoline efficiency only makes sense with the full two-step chain — skipping a step (or multiplying instead of dividing) can make an efficient EV look worse than a gas car, or vice versa.
Precision is not about showing off decimals. It is about making sure the shopping list, the machine setting, and the acceptance check are all describing the same physical quantity.
Pocket recap
Convert kWh/100mi to MPGe using the 33.7 kWh/gallon constant, then MPGe to L/100km using 235.215 — never collapse it into one multiply.
Keep the converter link nearby for the next time the same debate shows up in a group chat. Re-typing the factor from memory is how the wrong cousin of a unit sneaks back in.
Try the converters mentioned in this article
FAQ
What is the exact kWh per 100 mi to L/100km-equivalent factor here?+
EPA gasoline-gallon-equivalent: 33.7 kWh = 1 gallon; combine with 235.215 ÷ MPG = L/100km
Should I round partway through the calculation?+
No — carry full precision through the multiplication and round only the final answer, to the precision your tool, gauge, or spec actually supports.
What's the single biggest mistake people make with this conversion?+
Trying to convert kWh/100mi to L/100km with a single multiplication factor, when the real path runs through a reciprocal (efficiency to MPGe) and then another reciprocal (MPGe to L/100km).
This article was written by The Turbo Unit Converter engineering desk (Applied units & field metrology) and last reviewed on 2026-07-25 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.